One of the more important features in a cockpit is the Heads Up Display (“HUD”) whereby flight control and tactical information is projected onto the wind screen of the aircraft so that the pilot may receive the information without taking his eyes from the airspace in front of him. However, there has been a growing interest in moving away from HUD systems to NTE or to NTE-HUD systems with head mounted viewing and sensor components that may be attached to a pilot's earphones or to his helmet.
A NTE system is characterized by a small display screen that is suspended directly in front of one or both of the pilot's eyes such that the displayed virtual object or the image moves about the display screen as the pilot turns his head to look for other aircraft, to look at his other controls and instrumentation, etc. The NTE display is otherwise transparent such that the pilot may see through, or see past, the display.
It would be disconcerting, disorientating and annoying to the pilot if information being sent to the NTE display was constantly visible in his NTE display as he looks around him for other aircraft or for cockpit instrumentation. As such, a NTE display processor is programmed to register or conform the NTE display information or virtual object within a specific area within the cockpit such that when the pilot is looking at the area of image registration the NTE information is visible in his NTE display and when he turns, nods or cocks his head (i.e. yaw, pitch and roll), the NTE information moves in the opposite direction, and even out of view, until the pilot returns his head back to a normal flight position.
The image registration is typically established by attaching one or more markers or marker bars to physical locations in the cockpit. The markers may have a particular shape, a particular pattern or emit light at a particular frequency. The shape, pattern or frequency can be detected by a sensor attached to the pilot's NTE headset. The detected position of the marker then causes the NTE processor to render the display on the NTE display screen only when the pilot's head is in a desired viewing position range relative to the marker. Because the markers emit or reflect energy information they may be termed energy markers or information markers.
However, the registration process as practiced in the art has not been perfected. It has been noticed that the pilot's head movements may be very fast. Yaw movement has been determined to reach the 1000 degrees per second range compared to a nodding action (pitch) and cocking action (roll) which has been measured in the 400 degrees per second range.
Because of relatively rapid head motions, blurring of the NTE image or virtual object can occur regularly when a pilot moves his head. This is so because a NTE head positioning sensor only periodically updates the position of a pilot's head. If a rapid yaw motion should occur during the interstitial time period between head position updates, sequential information frames will be presented with an abnormally large physical separation in the NTE display, the size of which is a function of the head's travel time and velocity. This separation results in the horizontal blurring of the virtual object image as the image “swims” away from its registration. The longer the latency between head position measurements, the worse the distortion. Therefore, there is a need to improve an NTE display to minimize the distortion resulting from a pilot's head movement.